The invention relates to a filling pipe for filling a fuel tank, which has an antisurge tower, with fuel.
In addition to optimized space economy, the fuel tank of current motor vehicles at the same time has to offer the highest degree of passive safety. For this reason, the fuel tank is generally inserted into a region of the rear axle which is particularly well protected against mechanical damage. At the same time, fuel must not emerge under any driving conditions, in particular not even during overturning. In order to make possible convenient filling of the fuel tank despite this, the fuel tank is connected to a filling opening, which is arranged in the lateral rear region, by means of the filling pipe. The inflowing fuel passes through the filling pipe into the fuel tank and, at a sufficiently high level, into an antisurge tower inserted therein. In order to make it possible for the internal combustion engine to be sufficiently supplied, even under difficult driving conditions, the delivery unit does not suck up the fuel directly from the fuel tank but rather from the antisurge tower which surrounds the delivery unit. For this purpose, this antisurge tower is filled, by means of a pump, for example a sucking jet pump, continuously with fuel during operation, so that the antisurge tower is always sufficiently filled with fuel. As fuel consumption increases, the fuel tank, which surrounds the antisurge tower, is therefore emptied first of all and finally the antisurge tower itself is emptied.
A disadvantage here is that the fuel poured in after the fuel tank is completely emptied is initially unable to be sucked up by the delivery unit, since the fuel is first of all distributed in the fuel tank and the level remains so low that the required amount does not flow into the antisurge tower. Only relatively large amounts of fuel result in the antisurge tower being sufficiently supplied with fuel and thereby make the restoration of the operationally ready state possible. However, it is precisely during an emergency filling using a reserve can that the amount required for this purpose is, under some circumstances, insufficient.
It has also already been proposed to conduct the fuel flowing into the fuel tank through the filling pipe directly into antisurge tower, so that the latter is filled first of all and the overflowing fuel is subsequently distributed in the fuel tank. However, a disadvantage here is the fact that the overflowing of the antisurge tower causes a turbulent flow, with the result that the fuel tends to foam over and emit gases. At the same time, there is a delay in the length of time taken for filling the fuel tank, since in the meantime the process has to be interrupted and a delay made until the fuel has calmed down. However, during this time fuel vapors are able to escape unimpeded out of the fuel tank, which has to be avoided precisely in view of the health-endangering consequences of these fuel vapors. It has furthermore been shown in practice that large volume flows, which are conducted directly into the relatively small antisurge tower, are not suitable for reliable filling but rather that, in contrast, the greater part of the fuel is sprayed out or overflows and only a small part remains in the antisurge tower.